Mobile radio frequency (RF) chip designs (e.g., mobile RF transceivers) have migrated to a deep sub-micron process node due to cost and power consumption considerations. The design complexity of mobile RF transceivers is further complicated by added circuit function to support communication enhancements. Further design challenges for mobile RF transceivers include analog/RF performance considerations, including mismatch, noise, and other performance considerations. The design of these mobile RF transceivers includes the use of a voltage controlled capacitance and/or a tunable capacitor (e.g., a varactor), for example, to provide a voltage controlled oscillator.
Digitally controlled or voltage controlled oscillators may have very sensitive nodes where thermal noise may be converted to phase noise around an oscillation frequency. Biasing these nodes may negatively affect the oscillator by lowering the quality (Q)-factor of the tank circuit, thus increasing its phase noise. Some systems can implement resistive circuitry to reduce varactor noise contribution.